This application claims priority from Japanese patent application Serial No. 2000-282865 filed Sep. 19, 2000, the contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to a paper feeding apparatus, and more particularly, relates to a paper feeding apparatus wherein it is possible to prevent a image reading turbulence in a image reading device or the like.
2. Description of the Related Art
Conventionally, for example, in a image reading device, in the case where a lot of scripts are automatically carried and read, there is an automatic paper feeding mechanism (ADF). The automatic paper feeding mechanism comprises a pick mechanism which moves a plurality of sheets of paper mounted on a shooter to a specified preparing position; a separating mechanism which takes in the paper put on the preparing position one by one; and a feed mechanism which has a feed roller and a discharge roller for carrying the paper.
FIG. 8 is an description drawing of a conventional embodiment. In FIG. 8, to the feed mechanism, a feed roller 11 and a discharge roller 23 are provided. Furthermore, a driven roller 24 is provided corresponding to each of the feed roller 11 and the discharge roller 23.
At the feed roller 11, a feed roller gear 36 for driving the feed roller 11 is provided. Furthermore, at the discharge roller 23, a discharge roller gear 40 for driving the discharge roller 23 is provided. Then, the feed roller gear 36 is driven through a train of gears 34, 35 by a motor or the like. Furthermore, the discharge roller gear 40 is driven through a train of gears 37, 38, 39 by a motor or the like.
The paper such as a script is supplied to a reading position from the feed roller 11 and discharged by the discharge roller 23. This discharge roller gear 40 is driven by a train of gears 37, 38, 39 or the like, and therefore, there is a backlash between engaged gears. Because of this backlash, there has been such a case where the discharge roller slips and the paper momentarily stops when the rear end of the paper is separated from a pair of rollers (a feed roller 11 and a driven roller 24) just before the reading position.
This slip is caused by the fact  less than 1 greater than  in order to prevent a looseness of the paper at the reading position, the discharge roller 23 sends the paper a little faster than the feed roller 11 (the paper is pulled to the discharge roller 23 side), and therefore, a reaction is caused when the rear end of the paper is separated from the pair of rollers just before the reading position and  less than 2 greater than  the paper is kicked in the discharge direction by the above described pair of rollers when the rear end of the paper is separated from the pair of rollers just before the reading position.
In the case of the above described conventional embodiment, when the rear end of the paper is separated from the pair of rollers just before the reading position, a image turbulence has clearly been shown. Especially, in the case of a color scanner, it has been shown as a color drift, and shown more remarkably.
It is an object of the present invention to solve such conventional problems, and to prevent the image turbulence which is caused when the paper is separated from the feed roller.
A paper feeding apparatus of the present invention comprises a feed roller for supplying the paper to image reading position; and a discharge roller for discharging the paper, and to the above described discharge roller, a load in the rotational direction is provided for preventing the image reading turbulence at the time when the paper is separated from the above described feed roller. Therefore, it is possible to prevent the image turbulence which is caused by the slip of the discharge roller when the paper is separated from the feed roller.
Furthermore, the paper feeding apparatus of the present invention further comprises a discharge roller gear for driving the above described discharge roller; and a train of gears for driving the above described discharge roller gear. The above described load is provided at one of the train of gears for driving the above described discharge roller gear to eliminate the backlash between the above described discharge roller gear and the gear to which the above described load is provided. Therefore, even in the case where a load cannot be applied directly on the discharge roller, it is possible to apply a load on the discharge roller.
Furthermore, in the case of the paper feeding apparatus of the present invention, the above described load is preferably a compression spring that is provided between the discharge roller gear for driving the shaft of the above described discharge roller and the bearing of the above described discharge roller. Accordingly, it is unnecessary to provide a mechanism for eliminating the backlash, and it is possible to easily apply a load to the discharge roller by the compression spring.
Furthermore, in the case of the paper feeding apparatus of the present invention, the above described load is a torsion coil spring which comes into contact with the shaft of the above described discharge roller at the inside diameter. Accordingly, it is unnecessary to provide a mechanism for eliminating the backlash, and it is possible to easily apply a load to the discharge roller by the torsion coil spring.
Furthermore, in the case of the paper feeding apparatus of the present invention, it is preferable that the above described load is produced by pressing a body with the character of a spring onto the shaft of the above described discharge roller. Accordingly, it is unnecessary to provide a mechanism for eliminating the backlash, and it is possible to easily apply a load to the discharge roller by pressing a body with the character of a spring.